1. Field of the Invention
The system of the present application relates in general to the field of honeycomb core-stiffened composite structures.
2. Description of Related Art
Composite structures or panels often comprise honeycomb core disposed between and adhesively bonded to an inner skin and an outer skin. Such structures are desirable due to their high strength-to-weight ratio. It is often necessary to attach members, such as clips and the like, to honeycomb-stiffened structures. Accordingly, various attachment devices exist to affix members to honeycomb-stiffened composite structures.
FIG. 1 depicts a honeycomb-stiffened composite panel 101 comprising a honeycomb core, such as a honeycomb core 201 of FIG. 2, disposed between and adhesively bonded to an inner skin 103 and an outer skin 105. One way of attaching members to panel 101 is to adhesively bond a pad 107 or 109 to panel 101. Pad 107 includes a female threaded element 111 and pad 109 includes a male threaded element 113. Elements 111 and 113 are used to attach the member to pad 107 or 109, respectively. Except for elements 111 and 113, pads 107 and 109 are the same. Pads 107 and 109, however, are retained on panel 101 solely by the adhesive bond between pad 107 or 109 and panel 101. Thus, the adhesive bond between the pads, i.e., pads 107 and 109, and panel 101 may not be mechanically sufficient to retain the pads on panel 101. Moreover, the quality of the adhesive bond between the pads and panel 101 is adversely affected by improper preparation of panel 101 where the pads are to be attached.
Referring now to FIGS. 2 and 3, another way of attaching a member to a honeycomb-stiffened composite panel, such as panel 203, is through the use of a “potted insert.” Note that in FIG. 2, a portion of an inner skin 205 of panel 203 has been removed for clarity. A portion of honeycomb core 201 is removed and replaced with a threaded insert 207. Threaded insert 207 is “potted” in place using an adhesive portion 209. While this way of attaching members to panel 203 is effective, the weight added to panel 203 by adhesive portion 209 is often significant and undesirable in weight-sensitive applications.
Referring now to FIG. 3, a member may be attached to panel 203 by providing an attachment apparatus 301 that extends through panel 203. Core 201 is locally filled with an adhesive portion 303. A hole 305 is drilled through inner skin 205, adhesive portion 303, and an outer skin 307 of panel 203. Outer skin 307 provides a recess 309. A threaded rod 311 is attached to an inner element 315. Outer element 313 is disposed in recess 309 and threaded rod 311 is disposed through hole 305. An inner element 315 is threadedly engaged with rod 311 to affix apparatus 301 to panel 203. While this way of attaching members to panel 203 is effective, the weight added to panel 203 by adhesive portion 303 and apparatus 301 is often significant and undesirable in weight-sensitive applications.
There are many devices for and ways of attaching members to honeycomb core-stiffened composite panels well known in the art; however, considerable room for improvement remains.
While the system of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the system to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the system as defined by the appended claims.